1. Field of the Invention
This invention pertains generally to circuit interrupters and, more particularly, to circuit breakers including primary and secondary covers.
2. Background Information
Circuit interrupters, such as circuit breakers, are employed in diverse capacities in power distribution systems. A circuit breaker may include, for example, a line conductor, a load conductor, a fixed contact and a movable contact, with the movable contact being movable into and out of electrically conductive engagement with the fixed contact to switch the circuit breaker between an on or closed position and an off or open position, or between the on or closed position and a tripped or tripped off position. The fixed contact is electrically conductively engaged with one of the line and load conductors, and the movable contact is electrically conductively engaged with the other of the line and load conductors.
Circuit breakers may also include an operating mechanism having a movable contact arm upon which the movable contact is disposed, a pair of links, a main spring, a latch mechanism a cradle and a movable operating handle that extends outside of a housing for the circuit breaker. The cradle is pivotally disposed between the latch mechanism and the links. One portion of the cradle pivots with respect to the housing while another portion of the cradle has a latch ledge, which is latched by the latch mechanism.
It is known to employ latch mechanisms including a primary latch and a secondary latch. See, for example, U.S. Pat. Nos. 6,747,534 and 6,140,897.
It is also known to employ a secondary circuit breaker cover to cover internal accessories. This eliminates the need for the primary cover of the circuit breaker to be removed by the customer. To ensure that the circuit breaker is open or off when the customer removes the secondary cover, a mechanism is needed to trip open the operating mechanism when the secondary cover is removed.
U.S. Pat. No. 6,140,897 discloses a circuit breaker including a housing with an auxiliary device compartment therein into which may be inserted a key lock arrangement. The circuit breaker trip unit may include a plunger member which protrudes into the auxiliary device compartment and which, when actuated, causes the trip unit to actuate the circuit breaker operating mechanism to open the separable contacts. When the key lock is actuated, a slideable member interacts with the plunger member in the trip unit and maintains the trip unit in a configuration that prevents the separable contacts from engaging. Thus, as long as the lock member is maintained in the locked state, the circuit breaker may not be reset.
U.S. Pat. Nos. 6,052,047 and 6,232,855 disclose a molded case circuit breaker including a housing base and a primary cover disposed on the housing base. The primary cover has a recess therein for an auxiliary module which is disposed in the recess. A secondary cover is disposed on the primary cover for covering the recess when the auxiliary module is disposed therein. A combination manual trip and secondary cover interlock is provided which is accessible from outside of the secondary cover for manually opening the separable contacts or for automatically opening the separable contacts when the secondary cover is removed. The cover interlock member may be utilized to trip the circuit breaker by interaction thereof with a shaft either by downward motion when a push-to-trip actuation is required or by upward motion if the secondary cover is removed.
There is room for improvement in circuit breakers employing secondary covers.